CODE EXAMPLE FOR JAVASCRIPT

node.js socket.io send data with handshake

/* Client Side: */
//The query member of the options object is passed to the server on connection and parsed as a CGI style Querystring.
var socket = io("http://127.0.0.1:3000/", { query: "foo=bar" });


/*Server Side: */
io.use(function(socket, next){
    console.log("Query: ", socket.handshake.query);
    // return the result of next() to accept the connection.
    if (socket.handshake.query.foo == "bar") {
        return next();
    }
    // call next() with an Error if you need to reject the connection.
    next(new Error('Authentication error'));
});